Newt protein makes legs grow back

Newts can manipulate their bodies by turning cells into undifferentiated stem cells and then back into mature tissue again (Image: Anoop Kumar)

Scientists have found a key protein that helps newts regrow severed limbs and which may guide future research into human regenerative medicine.

Biologists have long been intrigued by the ability of newts and salamanders to renew damaged body parts. But how they do it has been unclear.

Now new research by a UK team publishing in the journal Science shows the role of a key protein nAG that's secreted by nerve and skin cells.

This plays a central role in producing a clump of immature cells, known as a blastema, which regrows the missing part.

The importance of nAG was demonstrated by the fact that even when a nerve was severed below the stump tip, which would normally prevent regrowth, the scientists were able to coax regeneration by artificially making cells produce the protein.

Dr Anoop Kumar and colleagues from University College London (UCL) say the finding "may hold promise for future efforts to promote limb regeneration in mammals".

A clear understanding of the molecular signals involved in blastema formation and limb regeneration could eventually allow medics to make similar patterns into cells of non-regenerating body parts.

"How soon this might be possible, particularly in humans, is anyone's guess but the addition of nAG to the repertoire of necessary factors is an important step forward," says Stocum, who writes about the research in the same issue of Science.

In effect, newts are able to manipulate their bodies by turning cells into undifferentiated stem cells and then back into mature tissue again.

It is a clever trick. But understanding how they do it does not mean humans will necessarily be able to copy them and regrow lost arms or legs, according to Professor Jeremy Brockes of UCL.

"It would be very desirable for regenerative medicine to understand the specification of the blastema and to try to recreate that in a mammalian context. But we are a long way away from being able to do that," he says.